It is well known that ordinary side mirrors have the disadvantage that it is not possible to encompass the so-called blind spot with them. A passing vehicle which is located in the blind spot cannot be seen in an ordinary side mirror. This can lead to dangerous situations in street traffic if a driver, not having perceived the vehicle located in his blind spot by means of a glance at his side mirror, pulls out to pass another vehicle. On account of the invisible blind spot, dangerous situations can also arise when traffic merges on freeways and highways as well as when a vehicle leaves a parking place.
Therefore, it has become familiar to provide a separate additional mirror for the blind spot and to mount it on the mirror surface of the normal side mirror. Such a side mirror shows, accordingly, two mirrors running at an angle to each other, of which the first mirror comprises the normal side mirror and the second mirror is intended to encompass the blind spot.
As opposed to the traditional side mirrors, such so-called angle mirrors permit the attainment of greater safety in street traffic. However, it has been shown that the angle mirrors are not free from disadvantages either, and for the following reasons. Mounting the additional mirror to the mirror surface of the normal side mirror reduces its effective size, and as a result the field of vision encompassed by the normal side mirror for the driver is reduced as well. In addition, it is a disadvantage that the mirror surface of the additional mirror must be located at an angle to the mirror surface of the normal mirror. This causes the appearance of a break at the point where the mirror surface of the normal side mirror ends and the mirror surface of the additional mirror begins, leading to a visual gap between the fields of vision of the additional mirror and the normal one. This visual gap, which is not to be avoided with the familiar angle mirrors, can be so large that, e.g., a motorcycle passing the vehicle "disappears," and the driver looking into his side mirror cannot perceive this motorcycle. Finally, the entire mirror image appears to the driver of the vehicle equipped with an angle mirror as an interrupted whole, on account of the visual gap, which is irritating and requires a rather long time for the driver to get used to such angle mirrors.